The present invention relates to optical disk recording apparatus for recording audio signals onto optical disks in digital representation. More particularly, the present invention relates to an improved optical disk recording apparatus which is arranged to temporarily store input digital audio signals into a buffer memory in synchronism with clock pulses reproduced from the input digital audio signals and then read out, from the buffer memory, the digital audio signals in synchronism with reference clock pulses, generated by an internal reference clock pulse generator, to thereby record the read-out audio signals onto an optical disk at a same sampling rate as the input digital audio signals, and which can appropriately reduce a wait time from a time point when an instruction for terminating the recording is given to a time when the recording is actually terminated in response to the instruction.
As an example of the optical disk recording apparatus for recording audio signals onto an optical disk in digital representation, the audio CD (Compact Disc) recorder has been put to actual use, which is constructed to record input audio signals onto a CD-R (CD Recorder/CD Write-Once) or CD-RW(CD Rewritable) disk in a CD format. Such an audio CD recorder accepts input of both analog audio signals and digital audio signals. When the input of digital audio signals has been selected, the audio CD recorder generally records the input digital audio signals onto an optical disk after having converted the sampling rate of the input digital audio signals to the CD sampling rate of 44.1 kHz. If the sampling rate of the input digital audio signals is the same as the CD sampling rate (e.g., if the input digital audio signals have been received from a CD), the input digital audio signals can be recorded as the so-called xe2x80x9cCD direct recordingxe2x80x9d without the sampling rate conversion. In the CD direct recording, 44.1 kHz clock pulse signals are first reproduced from the input digital audio signals. In synchronism with the thus-reproduced clock pulse signals, the input digital audio signals are temporarily written into a buffer memory and then the digital audio signals are read out from the buffer memory and recorded onto the optical disk. At that time, the clock pulses are frequency-divided to create 22.05 kHz clock pulse signals, and rotation of a spindle motor driving the optical disk is controlled in a PLL (Phase-Locked Loop) fashion so that a wobble frequency detected from the optical disk coincides with the frequency of the thus-created clock pulse signals. Also, the reproduced clocks are frequency-multiplied and then fed to a recording strategy circuit so as to finely adjust/control an irradiation time and irradiation start timing of a recording laser light beam.
However, because the above-mentioned conventional recording technique operates the recording strategy circuit by use of the reproduced clocks having a relatively poor accuracy (i.e., having relatively great time axial variations), the irradiation time and irradiation start timing of the recording laser light beam tend to be finely adjusted with a very poor accuracy relative to predetermined adjustment amounts, which would unavoidably result in degradation of recording signal quality and increased reading errors at the time of reproduction. Thus, it is now being proposed that the CD direct recording be carried out on the optical disk using, in place of the reproduced clock pulses, reference clock pulses generated by an internal reference clock pulse generator such as a crystal oscillator. More specifically, according to the proposed recording scheme, the 44.1 kHz clock pulse signals are first reproduced from the input digital audio signals so that the input digital audio signals are temporarily written into the buffer memory in synchronism with the reproduced clock pulses, and then 44.1 kHz clock pulse signals are created on the basis of the reference clock pulses generated by the internal reference clock pulse generator. Thence, the digital audio signals are read out from the buffer memory and recorded onto the optical disk in synchronism with the 44.1 kHz clock pulse signals based on the reference clock pulses. At that time, 22.05 kHz clock pulse signals are also created on the basis of the reference clock pulses, and the rotation of the spindle is controlled in the PLL fashion so that the wobble frequency detected from the optical disk coincides with the frequency of the 22.05 kHz clock pulse signals. In addition, the recording strategy circuit is controlled on the basis of the reference clock pulses so as to control the irradiation time and irradiation start timing of the recording laser light beam. By thus operating the recording strategy circuit on the basis of the highly accurate reference clock pulses, the proposed recording scheme provides for recording with high recording signal quality and hence reproduction with minimized reading errors.
But, because the reproduced clock pulses used to temporarily write the input digital audio signals into the buffer memory and the reference clock pulses used to read out the digital audio signals from the buffer memory are not synchronous with each other in the proposed recording scheme, and if the speed of reading from the buffer memory is higher than the speed of writing into the buffer memory, then the buffer memory would run out of data to cause a so-called xe2x80x9cbuffer underrunxe2x80x9d situation and thus the recording fails. To prevent the undesired buffer underrun, it is necessary to start the recording onto the optical disk only after a sufficient quantity of data have been stored in the buffer memory. For example, in the case of a CD whose recording length is 80 min. and for which the reproduced clock pulses differ from the reference clock pulses by 300 PPM, the following time difference would result between the time for writing all the data into the buffer memory and the time for reading all the data from the buffer memory:
300 (PPM)xc3x9780 (min).xc3x9760 (sec.)=1.44 (sec.)
Thus, in this case, there arises a need to start the recording onto the optical disk 1.44 sec. after the writing of the input signals into the buffer memory has been initiated in response to a user""s instruction for starting the recording, as illustrated in FIG. 2.
Further, according to the above-mentioned CD format, an inter-music-piece blank signal, indicative of a blank segment between adjoining music pieces (silent signal), can be recorded at the beginning of each track (e.g., each music piece) in a program area, by setting an index of Q subcode to xe2x80x9c0xe2x80x9d. Each inter-music-piece blank signal has one of predetermined lengths, i.e. two or more seconds for the first track and zero (i.e. no blank segment between the music pieces, is also selectable) and more seconds for second and succeeding tracks. In FIG. 3, there is shown an exemplary manner in which the inter-music-piece blank signals are recorded onto an optical disk. When a music piece (a single track) is to be recorded onto a CD-R or CD-RW disk with an inter-music-piece blank segment, the inter-music-piece blank signal is first recorded onto the optical disk and the music piece is recorded immediately after the recording of the inter-music-piece blank signal (namely, with one stroke). Assuming that the recording onto the optical disk is started 1.44 sec. after the user gives a recording start instruction to initiate writing of input signals into the buffer memory similarly to the above-mentioned, the recording start of the music piece would be delayed more than 1.44 sec. from the user""s recording start instruction because the recording onto the optical disk is started after the inter-music-piece blank signal recording. FIG. 4 shows a situation in which the inter-music-piece blank signal is recorded for two seconds in the above-mentioned manner. Namely, the recording onto the optical disk is started 1.44 sec. after the user gives the recording start instruction to initiate the writing of the input signals into the buffer memory, and the recording of the music piece is initiated after the inter-music-piece blank signal has been recorded for two seconds. Thus, a long time would be required from the time of the user""s instruction for starting the recording to the time when the recording is actually started in response to the instruction. This means that a long time would also be required from a time point when the user instructs termination of the recording to a time when the recording is actually terminated in response to the instruction, so that even when the user wants to remove the disk or reproduce the recorded contents from the disk immediately after the terminating instruction, the user has to wait for a long time.
Although not specifically mentioned above, the recording on the CD-R or CD-RW disk, in effect, would also require a considerable wait for servo pull-in operations (including seek operations) from turning-on of various servomechanisms to a time when the servomechanisms have been actually brought to readiness for the recording. If the user turns on the various servomechanisms 1.44 sec. after the recording start instruction to initiate the writing of the input signals into the buffer memory and then starts recording of the blank signal after completion of the servo pull-in operations, then the start of the music piece recording would be delayed further, with the result that an even longer time would be required from the time when the user gives the recording terminating instruction to the time when the recording is actually terminated in response to the instruction. In addition, the wait would be further prolonged by a time required for recording position information into a PMA (Program Memory Area) following the end of the input audio signal recording.
In view of the foregoing, it is an object of the present invention to provide an optical disk recording apparatus which is arranged to temporarily store input digital audio signals into a buffer memory in synchronism with clock pulses reproduced from the input digital audio signals and then read out, from the buffer memory, the digital audio signals in synchronism with reference clock pulses, generated by an internal reference clock pulse generator, to thereby record the read-out signals onto an optical disk at a same sampling rate as the input digital audio signals and which can appropriately reduce a wait from a time point when an instruction for terminating recording is given to a time when the recording is actually terminated in response to the instruction.
In order to accomplish the above-mentioned object, the present invention provides an optical disk recording apparatus comprising an input device that receives an input digital audio signal sampled by a predetermined sampling rate, an external reference clock pulse generator that reproduces a first reference clock pulse on the basis of the input digital audio signal, an internal reference clock pulse generator that generates a second reference clock pulse, a buffer memory that stores the input digital audio signal therein in synchronism with the first reference clock pulses, and that reads out a stored input digital audio signal therefrom in shynchronism with the second reference clock pulses, an operator operable by a user to give an instruction as to whether an inter-music-piece blank signal is to be recorded or not, the inter-music piece blank signal being capable of recording onto an optical disk before recording of the input digital audio signal read from the buffer memory, and a controller that, on the basis of the instruction from the operator, when the inter-music piece blank signal is to be recorded, makes to reduce a time interval from start of storing of the digital audio signals into the buffer memory to a start of recording of the digital audio signals onto the optical disk as compared to when the blank signal is not to be recorded.
When the inter-music-piece blank signal is to be recorded in the inventive optical disk recording apparatus, the start of the recording of the input digital audio signals onto the optical disk is delayed, so that a greater quantity of data would be stored in the buffer memory. Thus, even if the start of the recording onto the optical disk is advanced or moved up, there would occur no undesired buffer underrun; that is, the start of the recording onto the optical disk can be advanced, without involving inconveniences, as compared to when the inter-music-piece blank signal is not to be recorded. By thus advancing the start of the recording onto the optical disk, it is possible to significantly shorten a wait time from a time point when an instruction is given for terminating the recording to a time when the recording is actually terminated in response to the instruction. When an inter-music-piece blank signal of a relatively long recording length is to be recorded, control may be performed for starting the recording of the digital audio signals onto the optical disk substantially simultaneously with the start of writing of the digital audio signals into the buffer memory.
According to another aspect of the present invention, there is provided an optical disk recording apparatus which receives input digital audio signals of a predetermined sampling rate, temporarily stores the digital audio signals into a buffer memory in synchronism with clock pulses reproduced from the digital audio signals and then reads out, from the buffer memory, the digital audio signals in synchronism with reference clock pulses, generated by an internal reference clock pulse generator to thereby record the digital audio signals onto an optical disk at a same sampling rate as the input digital audio signals, which is also capable of recording an inter-music-piece blank signal, generated within the optical disk recording apparatus, onto the optical disk at the beginning of recording and then reading out the digital audio signals from the buffer memory for recording onto the optical disk following recording of the blank signal, and which comprises: an operator operable by a user to variably set a recording length of the inter-music-piece blank signal; and a controller that, on the basis of a user operation of the operator, makes to, when an inter-music-piece blank signal of a relatively long recording length is to be recorded, reduce a time interval from a start of writing of the digital audio signals into the buffer memory to a start of recording of the digital audio signals onto the optical disk as compared to when an inter-music-piece blank signal of a shorter recording length is to be recorded.
When an inter-music-piece blank signal of a long recording length is to be recorded in the inventive optical disk recording apparatus, the start of the recording of the digital audio signals onto the optical disk is delayed correspondingly, and a greater quantity of data would be stored in the buffer memory. Thus, even if the start of the recording onto the optical disk is advanced, there would occur no undesired buffer underrun, so that the start of the recording onto the optical disk can be advanced, without involving inconveniences, as compared to when an inter-music-piece blank signal of a shorter recording length is to be recorded. By thus advancing the start of the recording onto the optical disk, it is possible to significantly shorten a wait time from a time point when an instruction is given for terminating the recording to a time when the recording is actually terminated in response to the instruction. Note that when an inter-music-piece blank signal of more than a predetermined recording length is to be recorded, control may be performed for starting the recording of the digital audio signals onto the optical disk substantially simultaneously with the start of writing of the digital audio signals into the buffer memory.
The optical disk recording may be arranged to select, as the audio signals to be inputted thereto, from among digital audio signals of a sampling rate equal to a recording sampling rate of an optical disk, digital audio signals of a sampling rate different from the recording sampling rate of the optical disk and analog audio signals, and then record the input audio signals onto the optical disk after converting the sampling rate of the audio signals to coincide with the recording sampling rate of the optical disk. When the digital audio signals of the sampling rate different from the recording sampling rate of the optical disk or the analog audio signals are selected as the audio signals to be inputted, the control section performs control for starting recording of the audio signals onto the optical disk substantially simultaneously with a start of writing of the audio signals into said buffer memory, irrespective of presence/absence or recording length of the inter-music-piece blank signal.
For each of the above-mentioned types of input audio signals, a motor controller for controlling rotation of a spindle motor and a recording strategy circuit for performing fine adjustment/control of an irradiation time and irradiation start timing of a recording laser light beam, which are both provided in the optical disk recording apparatus, perform various predetermined control in synchronism with the reference clock pulses. Further, the optical disk recording apparatus may be constructed as an audio CD recorder, in which case the optical disk may be a CD-R disk or CD-RW disk.